Silicon-carbid refractory article.



'citizen of the United States, residin rx J. mom or me rams, new

YORK, ASSIGNOR TO THE OABBOBUNDUM SILICON-GRID BEEN: CTOEY TICLE.

12,211. No Drawing. I

To all whom z'tma concern:

Be it known t at I, FRANK J. Toma, a at Niagara Falls, Niagara county, New ork, have invented a new and useful Improvement in Silicon-carbid Refractory Articles, of which the following is a full, clear, and

exact description.

My invention relates to refractory arti cles, such as bricks furnace lin1ngs,&c.,

- formed of silicon carbid. This material has well known refractory properties, and requires a temperature of about 2220 C. to is of high value as a refractory material, but certain difiiculties have been encountered in its use. It has been used in two forms-first, that'of a pure silicon carbid article without a binder, such as described in my U. S. Patents Nos. 992,698 and 1,013,700. This type is of great refractory value, but is expensiveto manu-. facture.

The second form or type consists of silicon carbid grains or powder, bonded with a ceramic or other binder. The. difiiculty with this type is that it has been heretofore" impossible to roduce itwith the desired high fusion. omt or decomposing point on account of t e large pro phlrtion of binder that has been necessary. e proportion of binder in such cases has been from 20 per cent. u ward. In furnace linings silicon carbid as been used with a ,binder of 10 per cent. of fire clay and 10 per cent. of silicate of soda. This large percentage of binding material lowers thesoftening or fusing point so that the material is, often no more refractory thanthe best fire clay. Furthermore, the silicate of soda reacts with the silicon carbid at a hi h tem erature and decomposes it, thus furt er limiting the temperature to which the article can be subjected. With this large proportion of bind ing material, when exposed to the corrosive Specification of Letters fatent.

Patented Nov. '2', 19116.

Application filed y 8, 1813. Serial No. 785,981.

I have discovered that these difiiculties in the manufacture of silicon carbid articles of the .binder may be overcome by using a binder whichis inert toward silicon carbid at high temperatures especially when the bricks or articles are molded under great pressure. In such case a relatively small amount of binder may be used, such as would be very inefficient with themethods of molding and burning heretofore used; and in addition I reduce the absorptive property of the article and greatly increase the apparent density, especlally when the article is burned at relatively high temperatures, which fuse the bond and cause it to exert a maximum binding action.

In carrying out my invention in its preferred form, Lpreferably use silicon carbid in coarse, granulard'nrm, preferably of mix' tures of grains from -14-mesh up to about 150 mesh A mixture of equal parts of No. 16, 24, 36j'and 100 mesh has given good results. In certain cases it has been proved desirable to also add .finely pulverized sili con carbid to fill interstices and make the article more dense. The binder employed is preferably a kaolin or highly refractory fire clay. This is'composed principally of silica and aluminum, neither of which will react with silicon carbid at the softening slag. A binder is of silicon action of slags and gases, the binder beytween the grains is attacked below the de- As t e burning of refractory ware at these sired temperatures and 'ves a resistance much inferior to the artic es of pure silicon carbid above referred to. If on the other hand the amount of binding material is reduced to raise the melting point and crease its resistance, its mechanical strengt is very deficient and-the bricks or articles have no practical durability onresistanoe to wear or compression strains.

temperatures is considerably beyond the although I three tone or more to range of fire brick kilns or pottery kilns,

l have found it necessary to build a special kiln for this purpose. This kilnis built on the principle of an ordinary fire brick kiln ut is fired with bituminous coal under forced draft. The lining of the kiln may be made of silica brick or referably" of silicon carbid brick. This hig temperature" ma also. obtained by 'regeneratorsj A big ly oxidizing atmosphere; in the kiln should be avoided.

The articles may also be satisfactorily burned in the electric furnace; In'some cases they ma be given a preliminary burn-' ing in an or inary fire brick kiln, at ordi nary kiln temperatures of say between 1300 and 1400, and then put' in place in'the furnace where they are used and the burning completed in actual service. The best results are obtained however, if they are completely burned before being put' into service. I I

The brick or article resulting from the use of my invention has anapparent density of from,2.40 to 2.55 grams per cubic centimeter.

Its porosity is low, and its mechanical strength and hardness greatly exceeds ,that

of any bonded refractory silicon carbid-article heretofore produced.

On account of the closeness of its physical structure and small amount of. binder, thearticle presents a working surface of almost solid silicon carbid and shows a remarkable resistance to heat and the corrosive-action of slags and gases. In fact, it stands the action of slags and corros1ve gases substan: tially as well as an articleof pure silicon carbid. It can be used in oil furnaces, furnaces'usmg powdered coal, electrlc furnaces,

and various other metallurgical furnaces and in operations where high'temperatures are used. Its hardness and resistance also make it useful for refractory structures where there is abnormal abrasion or wear from moving charges or attrition of gases.

-The advantages of my invention will be apparent to those skilled in the art, since a ended silicon carbid brick or article is produced of much higher resistance both to heat, compression strains and'abrasion than has heretofore been possible.

I Changes may be made in the binder, the method of mixing. burning, etc., without departing from my invention.

claim I 1. A silicon carbid refractory article, com-,- posed of silicon carbid and a vitrified binder which is inert toward silicon carhid,-the silicon carbid'consisting of a variety of sizes 1 'of grains of such proportion as to give an apparent density of not less than 2.3 when pressed, said binder constituting less than of the silicon carbid to give an apparent density of not less than temperature of rifymg temperature of at least 1500 degrees 'cen'tigrade, and said article having an apparent density of not less than 2.3.

2. The herein described'process of making I a refractory article of silicon carbid, which consists in mix ng-a variety of sizes of grams in such proportion as 2.3 when pressed, with a vitrifiable binder which is inert toward silicon carbid, and in a quantityv which will constitute less than ten per cent. of the article. then subjecting the article to perature of not less than grade.

3. A silicon carbid refractory article, com-' posed of a variety of different sizes of grains of silicon carbid ranging from a relatively coarse ritto arelatively fine powder, and a vitrifie binder which is inert toward silicon carbid, and which'has a vitrifying temperature of at least 1500 degrees (1., and said article having an apparent density of not less than 2.3. v

4. A silicon carbid refractory article, composed of a variety of selected sizes of grains of silicon carbid ranging in size from a relatively fine powder to relative coarse grits, and a clay binder which is inert toward the silicon carbid and which has a vitrifying at least 1500 degrees (3., said article having an apparent density of not less than 2.3..

5. "The hereindescribed process of making a refractory article of silicon carbid. which consists in mixing a variety of sizesof grains of the silicon carbid ran ing between 14 and 150 mesh with a clay binder which is inert toward the silico-ncarbid and in a quantity which will constitute less than ten percent. ofthe article, then subjecting the article to pressure and firing itat a temperature of not less than 1500 degrees C., the mixture of the sizes of silicon carbid being in such pro- 1500 degrees centiportion as to give the article an'apparent FRANK J. TONE.

' Witnesses:

' C. H. Cnosswooo, R. B. MARLEY.

pressure, and firing it at a tem-' 

